Mobile network operators (MNOs) can locate RF interference issues in fiber-based mobile networks using real-time, high-resolution RF spectrum analysis over CPRI (Common Public Radio Interface), evolved eCPRI, etc. CPRI, eCPRI, etc. are standards that defines an interface between Radio Equipment Controllers (REC) and Radio Equipment (RE). CPRI and eCPRI allows replacement of copper or coaxial cables between a radio transceiver and a base station, such as via fiber. For example, EXFO's OpticalRF™ application provides access to the RF signal through the digital CPRI link available at the base station, located at the bottom of the cell tower or kilometers away as in a Centralized Radio Access Network (C-RAN) architecture. Technicians can quickly and accurately identify critical interference issues such as external RF interference, and internal and external Passive Intermodulation (PIM).
The detection of interferers in RF spectrum is a common task carried out by technicians in the field. Interference appears in spectrum as persisting peaks. The more powerful ones show up on an RF spectrum in just about any conditions. Other peaks are subtle and require careful tuning of the RF spectrum analysis equipment. An experienced technician will be able to adjust the Resolution Bandwidth (RBW), the Video Bandwidth (VBW), as well as other parameters to emphasize the particular interference being hunted for. The OpticalRF™ (ORF) application provides technicians with the speed, granularity, and clarity to identify what issues are present. ORF is a digital spectrum analyzer that extracts its information from a CPRI link instead of an analog coaxial cable. It can be used by mobile operators to measure/troubleshoot cell towers. ORF has various controls available in a spectrum analyzer: RBW, VBW, Center Frequency, Span, etc. To operate such an instrument, the user must be well trained and experimented, such as an RF expert. Mobile operators have a shortage of qualified personnel to operate such instruments.
Conventional analysis approaches can integrate some version of automated measurement, but this always revolves around the manipulation and visualization of a spectrum trace. Some automatically put markers on the trace with numbers on it, others put the measurements in a table next to the trace and so on. All this information centers around a spectrum trace, and this is overwhelming to a non-expert technician. As more and more antennas are installed, there is a shortage of skilled and experienced technicians able to analyze RF spectrum to find interference and other states of the antenna. There is, therefore, a need to automate the analysis of the RF spectrum to facilitate the work, i.e., turning up and troubleshooting a cell tower, of the technician who is not an RF expert.